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Integration of CCTAO/PDMS composite films into proximity capacitive sensor devices
(2026-12-01)
Bongkarn, Theerachai
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Panpho, Phakakorn
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Charoonsuk, Thitirat
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Vittayakorn, Naratip
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Pakawanit, Phakkhananan
Flexible capacitive proximity sensors are promising for contactless sensing applications, but their performance is strongly influenced by the dielectric properties and microstructure of the sensing layer. In this work, CaCu<inf>3</inf>Ti<inf>4-x</inf>A<inf>x</inf>O<inf>12</inf>/polydimethylsiloxane (CCTAO/PDMS, A = Nd3+ or Gd3+) composite films were developed as flexible dielectric layers for interdigitated capacitive proximity sensors. Nd- and Gd-doped CCTO ceramics were synthesized by a solid-state reaction method and incorporated into a PDMS matrix at different filler loadings. Structural analysis confirmed that the CCTAO ceramics retained the cubic CCTO phase after rare-earth substitution, while the composite films preserved the characteristic amorphous structure of PDMS with embedded ceramic fillers. The FESEM, EDS mapping and X-ray tomographic microscopy analyses showed that the CCTNdO/PDMS composite had a more uniform distribution of ceramic particles than the CCTO/PDMS system. The dielectric measurements demonstrated the improvement in the dielectric constant of the PDMS-based composites upon CCTNdO incorporation and also indicated that the composites did not exhibit any significant changes in their dielectric properties across the range of frequencies examined. The CCTNdO/PDMS films were found to show the negative capacitance response as a function of distance due to the electric-field shunting mechanism when used in an interdigitated capacitor sensor. The sensor with composition 10 wt% CCTNdO/PDMS had excellent performance with a maximum normalized capacitance change equal to −8.70%, which corresponds to a proximity sensitivity of around 0.42%/mm and an effective sensing range of around 20 mm. It is concluded that the optimization of the loading of the rare-earth material in a flexible PDMS matrix is an effective approach to achieve a compromise between the dielectric enhancement of the sensor and the dispersion of the filler and fringing-field interaction in the contactless capacitive proximity sensor.
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Estimation of Vertical Jump Height using Capacitive Sensing Method
(2023-01-01)
Kaewjumras, Yongyut
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Klongratog, Bhanupol
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Inboonma, Weerayut
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Sukprasertchai, Siwakorn
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Somdock, Nuttakrit
This paper presents a low-cost vertical jump height measuring device based on the time-of-flight technique. A capacitive mat was developed and used as a sensing element to sense the athlete's feet. The capacitive mat was made from aluminum foils that dimensions of the capacitive mat ware with a width of 50.3 cm x length of 70.6 cm. The signal conditioning circuitry that was used as an analog front-end for measuring the capacitive was also described. The time difference between when athletes jumped off and reached the ground was calculated by a microcontroller. The jump height was recorded and stored via the computer. A total of 27 athletes, weighted between 48 kg to 115 kg were used as a sample. The testing results have shown that the proposed system has a percentage difference of 18.16%.
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Capacitive sensor readout circuit based on sample and hold method
(2022-04-01)
Petchmaneelumka, Wandee
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Phankamnerd, Phirapong
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Rerkratn, Apinai
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Riewruja, Vanchai
This paper presents a capacitive sensor readout circuit using sample and hold method. The proposed readout circuit is used to convert capacitance from sensor to DC (direct current) voltage output. The basic structure of readout circuit consists of the pulse generator circuit, differentiator circuit, amplifier circuit, monostable I circuit, monostable II circuit, and sample and hold circuit. The proposed technique is based on the change of time constant from differentiator circuit corresponding to the measurement capacitance. The sample and hold circuit is used for sampling output voltage from differentiator circuit. The output voltage of the proposed readout circuit is proportional to measurement capacitance. The standard capacitors with different capacitance are used to test the proposed converter performance. Experimental results show that the proposed readout circuit can convert measurement capacitance to output voltage with satisfied values, good linearity and high sensitivity.
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Applying HF and VHF/UHF partial discharge detection for distribution transformer
(2019-01-01)
Maneerot, Sakda
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Kando, Masaaki
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Pattanadech, Norasage
This paper represents application of high frequency (HF) and very high frequency/ultrahigh frequency (VHF/UHF) partial discharge (PD) detection for a distribution transformer. A capacitive sensor is used to detect the HF electric field caused by charge transfer inside oil–paper insulation due to PD at the defect site, and an electromagnetic sensor or antenna is used for detecting electromagnetic PD transients in the air outside the investigated transformer in the near-field region. Three types of artificial PD sources in air and insulating liquid, which are corona discharge, surface discharge and air void discharge in pressboard, were investigated. Three identical distribution transformers were rated at 22 kV, 400 V and 50 kVA, and were designed and constructed. The first transformer was filled with mineral oil, the second was filled with natural ester and the third was filled with palm oil. The PD generated by the air-filled voids in the insulating papers and pressboards of these transformers with five different conditions were investigated, i.e., non-impregnated paper, impregnated paper for 3 hours, 6 hours, 9 hours and 12 hours. The impregnation process was done with 65◦C liquid temperature, and the pressure in the oven was around 5 mbar. From the experimental results, it can be concluded that the electromagnetic PD transients radiated from the corona discharge of both high-voltage (HV) and low-voltage sides in the air are in the VHF range, and surface discharge frequency is extended up to the UHF range. For the PD in the insulating liquid, the phase resolved PD (PRPD) pattern in the HF range is a valuable tool to characterize the PD sources. The PD in an air-filled void inside the insulating paper of the mineral oil transformer is obviously different compared with those of the natural ester transformer and the palm oil transformer. For the manufacturing of distribution transformers in this research, it is found that after the paper insulation is dried out, the impregnation process for a period of 9 hours is suitable for improving the oil–paper insulation with an acceptable PD level. This paper is the cross-field application by applying the antenna and communication theory for detecting the discharge problems in HV equipment.
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A versatile interface circuit for capacitive and resistive sensors
(2017-12-13)
Petchmaneelumka, Wandee
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Mano, Pitsini
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Wutikun, Tanatat
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Riewruja, Vanchai
This paper presents a circuit design technique for realization of a versatile interface circuit for capacitive and resistive sensors. The proposed method is based on the use of operation of relaxation oscillator. Time periods generated from two relaxation oscillators are employed for the reference signal and another sensing signal from sensor. The output signal obtained in the form of time period is proportional to the sensing value from sensor. The proposed approach provides the attraction in terms of simple configuration and low cost. The proposed circuit performances confirmed by the experimental results using commercial devices are agreed with the expected values.
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Simple capacitance-to-time converter
(2017-02-18)
Petchmaneelumka, Wandee
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Wutikun, Tanatat
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Rerkratn, Apinai
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Riewruja, Vanchai
A method for implementing of a capacitive sensor interfacing circuit is proposed in this paper. The time period generated from a simple relaxation oscillator is utilized to determine the time period obtained from the capacitive sensor. The output parameter of the proposed converter is in the form of the time period. The capacitance of the sensor can then be calculated using ratio metric operation. The proposed converter can linearly convert the capacitance from the sensor to the time period. The purpose of the proposed converter plays an attention in terms of simple configuration and low cost. Performance of the proposed scheme is demonstrated by experimentally implementation. The resulting confirmed that the performance of the proposed converter is in good agreement with the expected value.
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OTA-based capacitance-to-period converter for capacitive sensors
(2013-03-28)
Kanjanapart, Naratorn
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Cheypoca, Thepjit
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Riewruja, Vanchai
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Petchmaneelumka, Wandee
A simple design technique for realization of a capacitance-to-period converter based on operational transconductance amplifiers (OTAs) is presented in this paper. The proposed principle utilizes the behavior of astable multivibrator. The configuration of converter is implemented using commercial available and low cost devices. The obtained time period is proportional to sensing capacitance. The conversion gain of proposed scheme can be changed by electronic means. Circuit performances verified by experimental results are agreed with the expected values. © 2013 ICIC International.
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Simple interface circuit for resistive/capacitive sensors
(2013-01-01)
Tongcharoen, Jakkapun
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Petchmaneelumka, Wandee
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Cheypoca, Thepjit
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Rerkratn, Apinai
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Riewruja, Vanchai
This paper presents a method to realize interface circuit for resistive and capacitive sensors. The proposed circuit employs commercially available devices to generate the output signal in form of time period, which is linearly proportional to the both of sensing resistance and capacitance. Circuit configuration is simple and small in size. Experimental results verifying the performances of the proposed circuit are also included.

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